Unfortunately after about 8 hours of troubleshooting with different kernel options, I no longer have any saved logs of the incident with my Realtek 8139 adapter. However, with all releases of gentoo-sources 2.6.18 and the masked 2.6.19, the 8139 module and built-in kernel driver work erratically. When I would attempt to use the network adapter, it would only receive data while a keypress was present. For example, if I would hold the CTRL key, eth0 would appear to function normally. However, upon releasing this key and avoiding over keystrokes the network adapter stops transferring data. So take this bug report for what it's worth, and if you seek further information (logs, etc.) on this issue give me another few days, as I need this computer fully-functional until 12/29. Thank you.
Please post logs when you can use the system, and then reopen this bug. There's nothing we can do from just a small description.